A game that consists of a cookie that must be clicked repeatedly to make more cookies. It gives you the illusion that you are making cookies, but you are really not. Tumblr seems to be obsessed with it (around August 2013)

Tumblr user 1: OMG have you played cookie clicker yet, it ruined my life!
Tumblr user 2: What no but I'll check it out
Tumblr user 2 after playing Cookie Clicker: OMFG I CAN'T STOP CLICKING THIS COOKIE